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authorNed Forrester <nforrester@whoi.edu>2008-09-13 02:33:18 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-09-13 14:41:52 -0700
commit7e96445533ac3f4f7964646a202ff3620602fab4 (patch)
tree8c8dfd18cb0447cabd834e2b68d209c2e870be24 /README
parent8423597d676615f3dd2d9ab36f59f147086b90b8 (diff)
pxa2xx_spi: dma bugfixes
Fixes two DMA bugs in the pxa2xx_spi driver. The first bug is in all versions of this driver; the second was introduced in the 2.6.20 kernel, and prevents using the driver with chips like m25p16 flash (which can issue large DMA reads). 1. Zero length transfers are permitted for use to insert timing, but pxa2xx_spi.c will fail if this is requested in DMA mode. Fixed by using programmed I/O (PIO) mode for such transfers. 2. Transfers larger than 8191 are not permitted in DMA mode. A test for length rejects all large transfers regardless of DMA or PIO mode. Worked around by rejecting only large transfers with DMA mapped buffers, and forcing all other transfers larger than 8191 to use PIO mode. A rate limited warning is issued for DMA transfers forced to PIO mode. This patch should apply to all kernels back to and including 2.6.20; it was test patched against 2.6.20. An additional patch would be required for older kernels, but those versions are very buggy anyway. Signed-off-by: Ned Forrester <nforrester@whoi.edu> Cc: Vernon Sauder <vernoninhand@gmail.com> Cc: Eric Miao <eric.y.miao@gmail.com> Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Cc: <stable@kernel.org> [2.6.25.x, 2.6.26.x] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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